Curtain wall



April 6, 1965 R. A. FERRELL 3,176,306

CURTAIN WALL Filed May 6, 1960 6 Sheets-Sheet 1 N INVENTOR.

RUSSELL A. FERRELL gx BY K A TORNEY April 1965 R. A. FERRELL 3,176,806

CURTAIN WALL Filed May 6, 1960 6 Sheets-Sheet 2 INVENTOR. 2 RUSSELL A. FERRELL A TORNEY April 6, 1965 R. A. FERRELL CURTA I N WALL 6 Sheets-Sheet 3 Filed May 6, 1960 INVENTOR.

RUS ELL A. FERRELL 44 Az ATTORNEY Filed May 1960 R A. FERRELL CURTAIN WALL 6 Sheets-Sheet 4 IN V EN TOR.

RUSSELL A. FERR Ma a/124 TORNEY April 6, 1965 R. A. FERRELL CURTAIN WALL 6 Sheets-Sheet 5 Filed May 6. 1960 m m m m RUSSELL A. FERREILL /J [K IIZORNEY April 6, 1965 R. A. FERRELL CURTAIN WALL Filed May 6; 1960 6 Sheets-Sheet 6 fi H Ill, 1 ASQ I 11 G4 1 1/ 1 J c 2 O ll 1.1L 2 2 z l 1 ll II I IN V EN TOR. RUSSELL A. FERRELL BY /J AT ORNEY tal frame members. ported upon the building structure by slidable means United States Patent Ofiice 3,176,806 CURTAHN WALL Russell A. Ferrell, Pittsburgh, Pa., assignor to H. H, Robertson Company Filed May 6, 1960, Ser. No. 27,398 16 Claims. (Cl. 18934) The present invention relates to a wall structure and more particularly to a curtain wall construction adapted to possess unusual versatility for receiving panels, glazing, window sash, door frames and the like.

The present invention embodies the principles set forth in my co-pending application SN. 703,356 filed December 17, 1957, now Patent No. 2,949,981, and includes improvements which result in fewer structural elements, less total weight and a somewhat simplified frame assembly.

The present curtain wall is characterized by a relatively thin construction without departing from strength requirements and weathertight features. A minimized number of component elements is assembled into frames prior to erection on the building structure. When erected, each individual frame is free for relative movement in a single plane which is parallel to the building structure. Thermal expansion and contraction of the frames creates such movement. The present curtain wall has no exposed fasteners to detract from a finished appearance. Each individual frame can receive glazing, structural panels, window sash, door frames and the like and can be combined with masonry construction for pleasing architectural effects. The present curtain wall is readily adapted to variation in sizes of panels and sizes of glazing without change of the principal elements.

According to the present invention, a plurality of .individual frames are formedfrom vertical and horizon- Each frame is independently supwhereby each frame is free for relative movement only in a single plane parallel to the exposed building structure. The frame supporting means,for a single story frame, may comprise a pair of horizontal channels in any one or more of the individual frames can be removed from the building without affecting the remaining frames.

These objectives and advantages of the present invention will become apparent from the following detailed description by reference to the accompanying drawings in which:

FIGURE 1 is a perspective illustration of a typlcal building embodying the curtain wall of the present in- 'vention',

'FlGURE 2 is an exploded perspective illustration of the vertical and horizontal frame members prior to as sembly into a frame;

FIGURE 3 is a perspective illustration of two frames according to the present invention;

" FIGURE 4 is a cross-section view taken along the line present curtain wall; j

FIGURES 5, 6, 7 and 8 are cross-sectionviews taken respectively along the lines 5-5, d-6, 77 and 8-8 ,of FIGURE 1.-it will be observed that FIGURES 5, 6,

4-4. of. FIGURE 1 illustrating a vertical seam in the r 7 and 8, taken as a group, present a cross-section view of the entire single story portion of the building of FIG- URE 1;

FIGURE 9 is a cross-section view taken along the line 9-9 of FIGURE 1 showing the assembly of the present wall in combination with a masonry wall;

FIGURE 10 is a cross-section view taken along the line iii-19 of FIGURE lshowing a corner juncture between two facades employing the present curtain wall;

FIGURE 11 is a crosssection view taken along the 11-11 of FIGURE 1 showing a juncture of the present multistory curtain wall with a roof of a building;

FIGURE 12 is an exploded perspective illustration of a juncture between two frames illustrating slidable fastening means for securing multistory curtain wall frames of this invention to the side of a building;

FIGURE 13 is a perspective illustration of an anchor angle employed for slidably securing the present frames to a building surface;

FIGURE 14 is a side elevation of the top-to-bottom juncture between two curtain wall frames in a multistory building;

FIGURE 15 is a plan view of a side-by-side juncture between two curtain wall frames; and.

FIGURE 16 is a perspective illustration of a bolt and T-nut employed in the slidable fastening connections .wall includes a plurality of vertical elements called mullions 13 and horizontal elements called muntins 141-. Positioned between the mullions 13 and muntins M are glazing 15 and decorative panels 16 which may comprise metals such as stainless steel, bronze, aluminum and the like, porcelainized metals such as porcelainized steel and aluminum, natural materials such as marble, granite, and synthetic materials such as glasses, plastics and the like. i i

The building it includes a structural skeleton comprising vertical columns 17 and horizontal beams which.

are not seen in FIGURE 1 because they are embedded in concrete floors 18. The curtain wall. of this invention forms an outer sheath for the building 18.

The curtain wall of this inventioncomprises, as a basic structural unit, rectangular frames as illustrated in an explodedview in FIGURE 2. A pair of mullion elements 19, 2%? forms the vertical sides of each individual frame. One of the elements is identified as a clamped mullion element 19 and the other as a clamping mullion element m. The clamped mullion element 19 includes a web portion 22, a pair of flanges 23, 24 at one end and a single flange 25 at the other end. The flanges 23, 2 4 are offset from each other.

The clamping mullion element 2% includes a web 26, a pair of flanges 27, 28 which are coplanar and a fastenerreceiving slot 29.

The mullion elements 19, 26 preferably are aluminum extrusions which are available in any desired length and which can be cut to the desired size.

Muntins 3d comprise the horizontal components of the frame. Each muntin 3%) includes a Web 31 having a V fastener-receiving slot 32 at its outboard edge and, at its other edge, an upward flange 33 and a downward flange Patented Apr. 6, 1965 34. An arcuate fastener-receiving boss 35 extends between the web 31 and the downward flange 34.

' It will be observed in FIGURE 2 that at each end (indicated by the arrow 36) the upward flange 33 and downward flange 34 are cut back a distance equal to the width of flanges 24, 28 in order that the ends of the muntin 34 will engage the mullion elements 19, 29 in an assembled frame.

A plurality of selfatapping screws 37 are provided for securing the mullion elements 19, 2%) to the muntins 30. The self-tapping screws 37 pass through oaenings in the web 22, of the mullion elements 19, 20 and are received in the arcuate fastener-receiving boss and the fastenerreceiving slot 32 of the muntin 30. It will be noted that each individual frame is assembled prior to erection on the building structure.

The resulting individual frames are illustrated in FIG- URE 3 and designated by the numeral 38. Each of the individual frames 38 is independently supported upon the building structure in a slidable manner whereby it is free for relative movement in a single plane parallel to the exposed surface of the building structure. The clamping mullion element 20 of one frame is placed in meshing relation with the clamped mullion element 19 of an adjacent frame to form a mullion 13. A typical mullion is illustrated in cross-section in FIGURE 4.

It will be observed that the flange 27 of the clamping mullion element 20 engages the flange 23 of the clamped mullion element 19. A vertical retainer channel 39 extends lengthwise of the mullion 13 and is secured to the clamping mull-ion element 20 by means of a self-tapping screw 40 which is threadedly secured in the fastenerreceiving slot 29.

The vertical retainer channel 39 includes a central web 41, a pair of curved legs 42 with terminal beads 43. A recess 44 is formed between the terminal beads 43 and the curved legs 42. A triangular bead 45 is provided on the inner face of the web 39 to fit into the fastener-receiving slot 29 as an alignment index in order to predetermine the relative positions of the vertical retainer channel 39 with respect to the clamping mullion element 20. The fastening screw 44? penetrates the trianmtlar bead 45.

A flange 25 of the clamped mullion element 19 is main tained in frictional engagement with the inner surface of the central web 41 of the vertical retainer channel 39, It

- will be apparent from inspection of FIGURE 4 that the clamped mullion element 19 is frictionally positioned by the surface contact between the flange 25 and the inner surface of the central web 41, at one side, and, at the other side, between the flanges 23 and 27. It will further be apparent from inspection of FIGURE 4 that the two mullion elements 19, 20 are free for slidable movement with respect to each other. Thus the mullion 13 can adapt to expansion or contraction of the frame components without external manifestation of such movement.

In FIGURE 4, the adjacent frames are supporting glass sheets 15. To accomplish this, a fixed glazing head 46 is secured to each of the mullion elements 19, 29 by means of self-tapping screws 47. The glass 15 is held in frictional engagement between the fixed glazing bead 46 and the terminal beads 43 of the vertical retainer channel 39. A suitable caulking material, preferably rope caulking, is

provided on each side of the glass 15, in the recess 44 and also between the glass 15 and the side of the fixed glazing head 46.

At the'ends of the external surfaces of the curved legs 42 in'the vertical retainer channel 39 there appears a groove which receives r e-entrant flanges of a vertical cover cap 48 in a snap-fit engagement.

Single story embodiment In the single story embodiment of the present invention I prefer to support individual frames with respect to the building structure by. means of fixed channels which themselves are secured to the building structure at the top and bottom of the. single story. The upper or head channel 49 is illustrated in FIGURE 5. The head channel 49 is secured to a building soffit 50 by means of a bolt 51. The head channel 49 has a central web 52 which includes a number of external beads 53 which provide a suitable seal for the head channel 49. The head channel 49 includes a forward leg 54 which serves to retain the present frames and also serves as a flashing by virtue of its outwardly bent lower edge. The head channel 49 has a back leg 55 including a terminal head 56 serving as a supporting surface for the individual frames.

The upper muntin 34a has secured to it a Z-shaped closure element 57 including a flange which is secured to the central web 31a by means of a self-tapping screw 58. The Z-shaped closure element 57 includes an outboard terminal bead 59 which serves as a bearing to secure the individual frames within the head channel 49 at the forward side. The terminal bead 56 bears against the upper flange 33a of the muntin 30a.

At the bottom of the single story embodiment, as shown in FIGURE 8, a base channel 60 is provided which is secured to the sill 61 of the building by means of a suitable screw 62. The sill screw 62 extends through a central web 63 of the base channel on. A forward leg 64 of the base channel 60 has a rc-entrant flange 65 which serves to confine an individual frame with respect to the building structure. A back leg 66 has an inwardly extending head 67 which serves to support individual frames by beating against the upper flange 33b of the muntin 3011. An angle 68 is fastened to the lower muntin 39 by means of a screw 69 extending through the central web 31b. The angle 68 assures horizontal alignment of individual frames within the base channel 60.

It will be observed by inspection of FIGURES 5, 6, 7 and 8 (which form a representation of one complete frame) that the individual frame may be installed by sliding the entire frame upwardly into the head channel 49 and dropping the entire frame thereafter into the base channel 60. It will be observed that the entire frame is free for vertical upward sliding movement within the head channel 49. The individual frame units, however, are confined by the head channel 49 and the base channel 60 against outward or inward movement with respect to the exposed surface of the building structure while being free to expand and contract horizontally and vertically.

Two intermediate muntins 30c and 30d are illustrated in FIGURES 6 and 7. One structural panel 16 is secured at top and bottom between muntins 30a and 30c. Another structural panel 16 is secured between muntins 30b and 30d. The structural panels 16, as shown, may include an outer facing 70 of decorative, wear resistant material such as procelainized steel or aluminum, stainless steel, bronze, aluminum, copper, vinyl covered metals and the like. The facing sheet 70 is secured in a solid rectangular frame 71 which is preferably filled with suitable insulating materials such as fibrous glass, mineral wool and the like. The structural panels 16 are'retained along their back horizontal edge surfaces by means of the muntin flanges 33 and 34. The structural panels 16 are maintained along their exposed horizontal edge surfaces by means of a horizontal retainer 73. The horizontal retainer 73 includes a central web 74 and a pair of terminal beads 75. A triangular bead 76 is provided along the inner surface of the central web 74 to enter into the fastener-receiving slot 32 to maintain proper alignment between the horizontal retainer 73 and the muntin 30. A

' self-tapping screw 77 extends through the central web 74 and the triangular bead 76 and is threadedly engaged within the fastener-receiving slot 32.. A recess 7 8 appears between the terminal beads 73 and the exposed surface of the facing sheet 70. Suitable caulking material is provided within the recess 78.

A pair of lateral grooves 79 appears in the horizontal retainer 73 to receive re-entrant flanges of a horizontal cover cap 80 which is secured in a. snap-fit engagement.

Where glazing 15 appears in the present wall, a fixed glazing head 81 is secured to the muntin 300 by means of a screw 82. Caulking material is provided on both sides of the glass in the recess 78 and between the glass 15 and the side of the fixed glazing head 81. Along the bottom edge of the glass 15, the fixed glazing bead 81a is equipped with a channel-like depression to accumulate any moisture which may condense along the inner surface of the glass 15. A number of openings are provided in the base of the channel-like depression to permit accumulated moisture to drain through the fixed glazing bead 81a over the forwardly sloping surface of the muntin d. Weep holes 72 are provided in the fixed glazing bead 81a. A plurality of weep holes 83 in the horizontal retainer 73 permit moisture drainage to the outer surface of the building through a plurality of weep holes 84 which are provided in the horizontal cover cap 80 along its lower surface. All of the described weep holes 72, 83, 84 are provided in staggeredrelation in order that external pressures against the wall of the building will not cause accumulated moisture to be known into the interior space of the building. The weep holes 72, 83, 84 shown in FIGURE7 appear in the same section solely for the purpose of illustration.

Having now described in connection with FIGURES 5, 6, 7 and 8 the various muntins, the mullions will now be considered. A typical central mullion already has been described in connection with FIGURE 4. A terminal mullion element is shown in cross-section in FIG- URE 9 to illustrate the manner of securing the present single story frames in relation to a fixed masonry wall. The masonry wall is indicated by the. numeral 85. A vertical end channel 86 is secured through its central web 87 by means of a screw 88 which is fastened into the masonry wall $5. The vertical end channel 86 is identical in all respects to the base channel 60 illustrated previously in:FIGURE 8. The vertical end channel 86 includes a forward leg 89, a re-entrant flange 90, a back leg fl il and a terminal head 92. An

angle 93 is secured by means of a screw 94 to the central web 25 of a clamping mullion element 20. The terminal bead 92 bears against the flange 27 while the extended leg of the angle 93 bears against the re-entrant flange 91) whereby the frame is in slidable engagement with the vertical end channel 85 and is free to slide inwardly and outwardly solely in a plane which is parallel to the exposed building structure. 1 A vertical retainer channel 39 is secured to the clamping mullion element 20 by means of a screw .threadedly engaged in the screw-receiving slot 29. i The terminal beads 43 bear respectively against the forward leg 89 and the exposed facing sheet '70 of the panel 16. Suitable caulking material is provided in the recesses associated with the terminal beads 43.

Preferably a reglet flashing 35 is provided between the vertical end channel 86 and the masonry wall 85 to assure a weather tight seam. A less expensive yet effective seam may be achieved by means of suitable caulking compound.

A typical corner detail showing the juncture of two walls of either single story or multistory construction is presented in FIGURE 10. It will be noted that clamping mullion elements 21 are provided adjacent to one another in the corner assembly. Thus one of the frames abutting the corner includes two clamping mullion elements 20 and no clamped mullion element of the type i e which is indicated herein by the numeral 19. Each of the frames 33a, 38b is secured with respect to the building structure as heretofore described. A modified vertical retainer channel 96 is fastened to each of the clamping mullion elements 20 by means of a screw 97. It will be apparent that the modified vertical retainer channel 96 corresponds (as shown in phantom outline) to the vertical retainer channel 39 previously described. Only that portion of the vertical retainer channel 39 which includes a triangular bead and one curved leg and terminal bead is required. A corner cover cap 98 has terminal re-entrant flanges to permit a snap fit engagement with the modified vertical retainer channels 96. A sheet metal awasoe flashing strip 99 covers the corner juncture of the two clamping mullion elements 20 and is secured to each of 7 them by means of screws 1630.

Multistory construction A building roof 102 normally is provided and may comprise wood, metal, concrete, gypsum and the like. A cant 1 13 normally is provided around the perimeter of the roof 102. The roof 102 is supported upon a roof beam 1114 which spans the distance between vertical columns (not shown). A small angle 105 is welded to the outer flange of thereof beam 194. A round bolt-receiving opening 106 is provided in the exposed leg of the angle 105. An anchor angle 107 is bolted to the angle 105 by means of a threaded fastener 1% which extends through the angle opening 106.

The anchor angle 107 is illustrated in perspective in FIGURE 13. It will be seen that one leg of the anchor angle 1127 has a slotted screw-receiving opening 109 and the other leg has a pair of round screw-receiving open ings 110. l

A Z-shaped flashing 111 having two flanges 112, 113 is secured to the roof 102 by means of a screw 114 extending through the flange 112. The central web of the Z-sh aped flashing 111 is substantially parallel to the bottom of the roof 1192. The depending flange 113 is substantially parallel to the exposed surface of the building structure and serves to support the upper edge of the topmost frames.

An angle strip 115 is secured to the sloping upper surface of the muntin 30 by means of a screw 115. A hori zontal retainer '7 3 is secured to the muntin 30 and provides a slidable engagement with the depending flange 113 which abuts the upright leg of the angle strip 115.

. A pair of slotted holes 117 is provided in the clamped mullion element 19 in alignment with the round holes The exposed leg of the anchor angle 107 abuts the central web of the clamped mullion element 19. A portion of the flange 23 (see FIGURE 2) on the inboard side of the clamped mullion element 19 is cut away to achieve the described abutting relationship which will be further described hereinafter in discussions of FIGURE 12.

It will be, apparent from FIGURE 11 that the anchor 1 angle 1117 is free to move horizontally with respect to the building structure by virtue of the slotted opening 1119. Similarly the frame is free to move vertically with respect to the anchor angle 107 by virtue of the slotted openings 117. Thus the entire individual frame is free to move horizontally and vertically over a limited distance with respect to the building structure. The movement is confined to a single plane which is parallel to the exposed building structure.

Built up roofing, usually in the form of plies of tar paper 121 is applied over the cant 103 and roof 102. A T-shaped gravel stop 122, sometimes called a coping, has a horizontal flange 123 and a vertical flashing 124. The gravel stop 122 is secured to the building by means of a screw 125 extending through the fiange'123. Additional built up roofing plies 126 are provided above the flange 12.3 to secure a watertight roof covering. it

FIGURE 12 presents an explodedperspective illustration of side-by-side frames showing in greater detail the method for securing the frames to the building structure. It will be observed that the clamping mullion element 20 of the left-hand frame is secured to the building structure by means of an anchor angle 107. Similarly the clamped mullion element 19 of the right-hand frame is secured to the building structure by means of an anchor angle 107. ,A portion of the flange 27 (of the clamping mullion element 20) is cut away to receive the anchor angle 107. Similarly a portion of the flange 23 (of the clamped mullion element 19) is cut away to receive an anchor angle 107.

When the left-hand frame and the right-hand frame of FIGURE 12 are mounted upon a building structure, the flange 23 is in slidable abutment with the flange 27. A vertical retainer 39 thereafter is secured to the clamping mullion element 20 by means of screws which extend through openings 132 and into the fastener-receiving slot 29 of the clamping mullion element 20.

As heretofore pointed out, a triangular bead 4:; of the vertical retainer engages the fastener-receiving slot 29 as an alignment index. A vertical line 134- is provided on the outer surface of the central web of the vertical retainer 39 opposed to the triangular bead 45 to aid in aligning the fastener-receiving openings 132. Similarly a horizontal line 135 is provided on the outer surface of the horizonta retainer 73 opposed to the triangular bead 76 to aid in aligning fastener-receiving openings 77.

The assembled adjacent frames are shown in a fragmentary cross-section in FIGURE 15. There a generally rectangular plate 128 is secured to the building structure, indicated by the numeral 129 by means of bolts 108 which also extend through slotted openings in anchor angles 107. It will be observed that the clamping mullion element 20 and the vertical retainer channel 39 serve to clamp in slidable engagement the clamped mullion element 19.

FIGURE 14 illustrates in side elevation the top-tobottom juncture of two frames in a multistory building.

A generally rectangular plate 128 is secured to a concrete floor 18 by means of a concrete insert spring nut 130 and bolt 108. A pair of angle anchors 107 is slidably secured to the rectangular plate 128 by means of the bolts 103. Clamped mullion elements 19 from the upper frame and lower frame are illustrated. It will be observed from the position of the T-nut screws 120 with respect to the slotted screw-receiving openings 117 of the upper frame that the weight of the frame inherently allows the clamped mullion elements 19 to slide until the T-nut screws 120 are located at the top of the slotted openings 117. At the upper end of the lower frame, the T-nut screws 120 are positioned midway in the slotted openings 117 to allow for thermal expansion and contraction.

A small gap 131 is provided between the upper and lower frames to accommodate thermal expansion. The gap 131 may range from about Aa-inch to /2-inch where the frames correspond to a single story in height. Where an individual frame extends over two or more stories in height, a larger gap 131 will be provided to accommodate greater expansion. The vertical retainer channel 39, as shown in FIGURE 14, extends over the gap 131 from the lower frame through the upper frame. To accommodate uneven thermal expansion properties, the screw-receiving openings 132 in the vertical retainer channel 39 preferably are slotted. A further gap 136 is provided between the top of one length of vertical retainer channel 39 and the bottom of the next higher length of vertical retainer channel 39.

Referring once more to FIGURE 12, the juncture of a muntin 30 with a mullion element 19 (or 20) appears more clearly. As indicated by the arrow 36 at the juncture, a portion of the flanges 33, 34 of the muntin 30 is cut away to receive the flange 24 of the mullion element 19 whereby the web 31 of the muntin 30 abuts the web 22 of the clamped mullion element 19. The corresponding structure is illustrated in phantom outline for the clamping mullion element 20.

The horizontal retainer 73 is cut to the same length as the muntin 30 and, at its ends, abuts the center web' 22 of the mullion element 19. Similar structure is illustrated in phantom outline for the mullion element 20.

In order to accommodate the horizontal retainer 73, a slot 133 is cut in the vertical retainer channel 39. Thus the terminal beads 74 and 43 are aligned for engagement with an inserted panel or glazing.

Each individual frame is entirely assembled before installation on the building structure. That is, the necessary glazing and structural panels are inserted within each frame and secured therein top-and-bottom. by means of the horizontal retainers 73. As each new frame is affixed to the building structure, the vertical retainers 39 are applied over the juncture of the mullion elements 19, 20 and are aligned with the horizontal retainers to secure the panels or glazing. It will be observed that the flanges 33, 34 of the muntins 30 and the flanges 24, 28 of the mullion elements 19, 20 present a coplanar surface to serve as a back engagement surface for the panels and glazing inserts.

From the foregoing description, the versatility of the present curtain wall construction should be apparent. The principal components include mullion elements 19, 20, muntins 30, horizontal retainers 73 and vertical retainer channels 39. With these standard components, it is possible to assemble a weather tight curtain wall in a wide variety'of architecturally varying configurations and appearances. These recited standard components preferably are formed as extrusions of aluminum in standard lengths which can be cut to the required length for any desired installation. The frame assembly enables the building erector to apply preassembled structural frames to a building structure without requiring glazing and panel installation on the site. If desired, the glazing and structural panels may be installed in assembled frames 38 after the frames have been secured to the building structure.

To replace any of the structural panels after the building has been erected, the associated vertical and horizontal cover caps 48, are removed. The associated vertical and horizontal retainers 39, 73 thus exposed, are removed by withdrawal of the screws 40, 77 and the structural panel is free for removal and replacement.

In the appended claims, the phrase structural panels is employed to include panels, glazing and assembled window frames and door frames.

According to the provisions of the patent statutes, I have explained the principle, preferred embodiment and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a curtain wall for a building structure comprised of a plurality of generally rectangular frames, each frame being formed from a pair of vertical mullion elements and a plurality of horizontal muntins, structural panels secured within each frame, the improvement in said frames comprising said muntins and mullion elements having co planar rear flanges retaining said structural panels along 7 the periphery thereof, said mullion elements including (1) a clamping mullion element having a laterally extended rear flange and a fastener-receiving front portion, and (2) a clamped mullion element having a laterally extended front flange and a laterally extended, inwardly offset rear flange engaged with the said rear flange of said clamping mullion element, a vertical retainer channel secured to said clamping mullion element front portion and friction ally engaging the front flange of a clamped mullion element of an adjacent frame, said clamping and clamped mullion elements being in contact only along the surfaces of the said laterally extended rear flanges thereof, each said frame being independently slidably secured to said building structure to permit relative movement in a single plane parallel to the exposed building structure upon thermal expansion and contraction.

2. In the curtain wall improvement of claim 1, said vertical retainer channel having curved leg portions and terminal beads which peripherally engage the front faces of said structural panels.

3. In the curtain wall improvement of claim 2, a vertical cover member having a central web and re-entrant leg portions engaged in snap-fit relation with the said curved leg portions to cover the said vertical retainer channel.

4. The curtain Wall improvement of claim 1, wherein the fastener-receiving front portion of the said clamping mullion element comprises a vertical slot and the said vertical retainer channel has an inwardly extended head which is engaged within the said vertical slot as a positive alignment means for the clamping mullion element and the vertical retainer channel.

5. In a curtain wall for a building structure comprised of a plurality of generally rectangular frames, each frame being formed from a pair of vertical mullion elements and a plurality of horizontal muntins directly fastened thereto, structural panels secured within each frame, the improvement in said frames comprising said niuntins and mullion elements having coplanar rear flanges retaining said structural panels along the periphery thereof, said muntins having a central web portion extending forwardly from said rear flanges and terminating in a horizontal fastener-receiving front portion, each said frame being independently slidably secured to said building structure to permit relative movement in a single plane parallel to the exposed building structure upon thermal expansion and contraction, a vertical retainer channel secured to the front portion of a mullion element of one frame and frictionally engaging the adjacent mullion element of an adjacent frame, and a horizontal retainer channel fastened to the said screw-receiving front portion of each said muntin and having a central web portion and a pair of legs peripherally engaging the front faces of said structural panels.

6. The curtain wall improvement of claim wherein the terminal portions of the rear flanges of each muntin are cut away to receive the rear flanges of said mullion elements.

7. The curtain wall improvement of claim 5 wherein an arcuate fastener-receiving boss is provided on the muntins between the central web and one rear flange thereof, and wherein the ends of each muntin are secured to a mullion element by means of two screws extending through said mullion element, one of said screws being fastened in said arcuate fastener-receiving boss and the other being fastened in the said fastener-receiving front portion of the muntin.

8. The curtain wall improvement of claim 5 wherein at least one of said structural panels comprises a glazing pane peripherally secured against the legs of said horizontal retainer channel by means of fixed glazing beads.

supported from said coplanar rear flanges.

, 9. The curtain wall improvement of claim 8 wherein, a horizontal cover channel is secured to said horizontal retainer channel and the fixed glazing bead securing the means for the muntin and the horizontal retainer channel.

11. In a curtain wall for a building structure comprised of a plurality of generally rectangular frames, each frame being formed from a pair of vertical mullion elements and a plurality of horizontal muntins, structural panels secured within each frame, the improvement in said frames comprising said muntins and mullion'elements having coplanar rear flanges retaining and structural panels along the periphery thereof, said rnuntins having a central web portion extending forwardly from said rear flanges and terminating in a horizontal fastener-receiving front portion, said mullion elements including (1) a clamping mullion element having a laterally extended rear flange and a fastener-receiving front portion and (2) a clamped mullion element having a laterally extended front flange and a laterally extended, inwardly offset rear flange engaged with the said rear flange of said clamping mullion element, said clamping and clamped mullion elements being in contact only along the surfaces of the said laterally extended rear flanges thereof, each said frame being independently slidably secured to said building structure to permit relative movement in a single plane parallel to the exposed building structure upon thermal expansion and contraction, a vertical retainer channel secured to said clamping mullion elements front portion and frictionally engaging the front flange of a clamped mullion element of an adjacent frame, a horizontal retainer channel fastened to the said fastener-receiving front portion of each said muntin, said horizontal and vertical retainer channels each having a central web and a pair of legs which peripherally engage the front faces of said structural panels.

12. The curtain wall improvement of claim 11 wherein the legs of said vertical retainer channels are cut away to receive the ends or" said horizontal retainer channels in abutment with said mullion elements.

13. The curtain wall improvement of claim 12 wherein said vertical retainer channel has a central web, a pair of curved legs and terminal beads, the said terminal beads forming a coplanar bearing surface with the ends of the legs of said horizontal retainer channel, said coplanar bearing surface peripherally retaining said structural panels.

bottom edge of said glazing pane provides a horizontal 14. The curtain Wall improvement of claim 13 wherein a strip of caulking material is provided between said coplanar bearing surface and the front edges of said structural panels.

15. The curtain wall improvement of claim 11 wherepanels and said cover members.

16. Curtain Wall assembly means associated witha curtain wall frames of generally rectangular configuration, each frame being formed from a pair of vertical mullion elements and a plurality of horizontal muntins, structural panels secured within each frame, the said muntins and munnion elements having coplanar rear flanges retaining the said structural panels along the periphery thereof, the said mullion elements of each frame including a clamping mullion element and a clamped mullion element, the said clamping mullion element of one frame being engaged with a said clamped mullion element of a laterally abutting frame; 7

the said curtain wall frames each having their upper portion received within the said horizontal head channel and their bottom portion received in the said base channel, whereby the said frames may be 11 12 slid laterally within the said head and base chan- 2,946,414 7/60 Gordon et al 18936 nels for sequential assembly therein. 2,949,981 8/ 60' Ferrell 18934 2,963,126 12/60 Cudini 189-34 References Cited by the Examiner 2,971,616 2 61 Bayley 1s9 34 UNITED STATES PATENTS 5 2,976,970 3/61 Toney 18934 2,985,263 5/61 Maciunas 189-75 X Re. 24,133 3/56 Bloedow 189-36 3,057,444 10/62 Walberg 189-75 X 1,569,144 1/26 Scarnrnell 5078 2,885,040 4/59 Gms an 189 34 BENJAMIN BENDETT, Primary Examiner. 2,914,145 11/59 136118011 189-4 10 JACOB 1. NACKENOFF, RICHARD W. COOKE, 2,916,108 12/59 Gartner 189- 4 -IOEL REZNEK Examiners 2,944,641 7/60 Peterson 189-34 

1. IN A CURTAIN WALL FOR A BUILDING STRUCTURE COMPRISED OF A PLURALITY OF GENERALLY RECTANGULAR FRAMES, EACH FRAME BEING FORMED FROM A PAIR OF VERTICAL MULLION ELEMENTS AND A PLURALITY OF HORIZONTAL MUNTINS, STRUCTURAL PANELS SECURED WITHIN EACH FRAME, THE IMPROVEMENT IN SAID FRAMES COMPRISING SAID MUNTINS AND MULLION ELEMENTS HAVING COPLANAR REAR FLANGES RETAINING SAID STRUCTURAL PANELS ALONG THE PERIPHERY THEREOF, SAID MULLION ELEMENTS INCLUDING (1) A CLAMPNG MULLION ELEMENT HAVING A LATERALLY EXTENDED REAR FLANGE AND A FASTENER-RECEIVING FRONT PORTION, AND (2) A CLAMPED MULLION ELEMENT HAVING A LATERALLY EXTENDED FRONT FLANGE AND A LATERALLY EXTENDED, INWARDLY OFFSET REAR FLANGE ENGAGED WITH THE SAID REAR FLANGE OF SAID CLAMPING MULLION ELEMENT, A VERTICAL RETAINER CHANNEL SECURED TO SAID CLAMPING MULLION ELEMENT FRONT PORTION AND FRICTIONALLY ENGAGING THE FRONT FLANGE OF A CLAMPED MULLION ELEMENT OF AN ADJACENT FRAME, SAID CLAMPING AND CLAMPED MULLION ELEMENTS BEING IN CONTACT ONLY ALONG THE SURFACES OF THE SAID LATERALLY EXTENDED REAR FLANGES THEREOF, EACH SAID FRAME BEING INDEPENDENTLY SLIDABLY SECURED TO SAID BUILDING STRUCTURE TO PERMIT RELATIVE MOVEMENT IN A SINGLE PLANE PARALLEL TO THE EXPOSED BUILDING STRUCTURE UPON THERMAL EXPANSION AND CONTRACTION. 